The effect of infill quantity and contamination on the performance of second generation sandfilled synthetic turf sports surfaces was investigated in a laboratory study. Three 1 m 2 test surfaces were constructed by placing synthetic turf over a stonetar-macadamrubber shockpad sub-base. Ball rebound, ball roll, surface rebound hardness and rotational resistance of a dimpled rubber sole were measured for a range of infill quantities (0-35 kg/m 2) and infill contamination concentrations (0, 10 and 20%). Increasing infill quantity increased hardness, reduced ball rebound and reduced rotational resistance linearly (p < 0.01). Ball deceleration increased up to 10 kg/m 2 after which there was no further significant increase in the range tested. An optimum infill quantity of 25-30 kg/m 2 , based on performance characteristics and the length of fibre above the infill, was identified for the synthetic turf surface tested. Increasing contamination also increased ball deceleration and reduced infiltration rate and kept surfaces wetter for longer during drying (p<0.001), resulting in conditions suitable for moss and algae formation. Maintenance, including regular brushing and monitoring of infill quantity is required to ensure even distribution of the correct quantity of infill and the minimisation of infill contamination in all in-filled synthetic turf surfaces.